Your VO2 max is like a '401(k) for longevity' — here's how to invest in it for better heart health and a longer life

• VO2 max is a trendy stat for measuring your fitness, and it can help improve longevity too.  
• Having a higher VO2 max is good, but more important for health is how the number changes over time. 
• Diversify your "fitness portfolio" without getting bogged down in data by training smarter. 

Forget about a big bench press or heavy squat. If you want to show off your fitness cred, a specific smartwatch screenshot is the new gym selfie.

Once reserved for exercise science nerds, a stat called VO2 max — a measure of how well your heart performs during exercise — is trickling into the mainstream.

Self-appointed anti-aging gurus like Bryan Johnson enthusiastically share their VO2 max stats on X (formerly Twitter), ostensibly as proof that their lifestyle routine is working, and makes them fitter than most teenagers.

Now, internet forums dedicated to longevity are filling up with people sweating over their Apple Watches, asking each other if their numbers measure up, or desperately seeking advice to fix less-than-impressive measurements to shore up their health.

It's true: knowing this metric and working to improve it could, in theory, help you to unlock a longer, healthier life. It is also hard to measure — and that is a blessing for the growing health tech sector, with companies rushing to help the longevity-focused elite calculate and improve their own VO2 max.

"It's very similar to a 401(k) in a way. If you are lucky or smart and you start saving for 401(k) at the age of 20, you have a much better chance to save a lot of money," anti-aging researcher Gil Blander, who is also the founder and chief scientific officer at personalized health tech company InsideTracker, told Business Insider. "If you are starting at the age of 70, it's good, but it's much better to start earlier."

Keeping tabs on your VO2 max, and especially how it changes over time, can help you get the most out of your workouts, and train for optimal heart health.

However, putting too much stock in a single data point can backfire if you're not also taking into account other metrics and lifestyle factors, longevity researchers warn. There's a way to use VO2 max to improve heart health and fitness without getting too bogged down in the data.

What is VO2 max and how is it measured?

VO2 max refers to the maximum amount of oxygen your body can use during aerobic exercise — in other words, how well your heart can circulate oxygenated blood to your muscles, and how well your muscles can pull out that oxygen for energy.

"It's traditionally considered a marker of endurance. So you have a higher VO2 max, you have a better endurance capacity," Blander said.

It was coined in 1923 by British physiologists Archibald Hill and Hartley Lupton. The term derives from the quantity in volume (the "V"), oxygen (O2, the chemical symbol for the oxygen molecule), and the abbreviation of "maximum."

It's typically described as milliliters of oxygen consumed per minute per kilogram of body weight.

For instance, the VO2 max of an active woman might be around 35 mL/kg/min, according to Cleveland Clinic. Men tend to have a slightly higher VO2 max, so an example for an active man could be around 42 mL/kg/min. These numbers hold true to around age 45, after which they start to dip. Unless you take your exercise seriously — it's possible for elite athletes in their 80s or beyond to have a VO2 max as good or better than people decades younger. One 2015 case study, for instance, found an 80-year-old man with a VO2 max of 50 mL/kg/min, comparable to a sedentary 20-year-old or active 35-year-old.

But it doesn't just matter for working out. How well your body uses oxygen can point to how well your heart is functioning overall, and how healthy it is under stress, according to Dr. Edo Paz, a cardiologist at White Plains Hospital and senior vice president of medical affairs at the digital health company Hello Heart.

Paz said VO2 max is most accurately measured with a stress test, which can also assess potential heart problems, such as issues with the valves.

It can be tough to accurately measure VO2 max at any given moment without heading into a lab, according to Paz, but you may not need to. Noting changes over time can indicate if your heart health is improving, he said.

Your VO2 max can tell you a lot about how your heart is aging

VO2 max can be a shorthand to help assess and lower your risk of dying early from illnesses like heart disease, diabetes, and cancer.

"If you have higher VO2 max you have a much better chance based on our data analysis to live better, longer, which is amazing," Blander said.

"I like to diversify my training portfolio. We need to do the majority of our investing at a lower intensity and some at a higher intensity to improve maximum efficiency"

— Mike Thomson, Life Time Overland Park personal trainer

Put simply, it can be a single number that gives you a sense of where you stand in terms of fitness now, and the odds that you'll keep being healthy and fit in the future.

"I like to think of it as a 'score' of your cardio and fitness potential. The higher your score, the greater your longevity," Mike Thomson, personal trainer and run coach at Life Time Overland Park, told Business Insider.

VO2 max also plays an important role in making sure you can keep up with the demands of day-to-day life even beyond your workouts, explained exercise physiologist Kate Baird. Your VO2 max tends to decrease as you get older, which over time can make it harder to do simple activities, according to Baird.

"If you're already at a low level, you'll start to feel those declines. Walking a few blocks down the street feels hard or a leisurely bike ride doesn't feel so leisurely," she said. "Keeping fitness high helps you maintain autonomy and translates to a longer life."

How to diversify your training portfolio for a stronger VO2 max

In terms of boosting VO2 max, Thomson also reached for money management as a metaphor for heart health longevity.

If VO2 max is your fitness retirement plan, training it can be similar to investing with a combination of strategies for best results.

"I like to diversify my training portfolio," he said. "We need to do the majority of our investing at a lower intensity and some at a higher intensity to improve maximum efficiency," Thomson said.

A combination of both high and low intensity, in a ratio of around 80% easy and 20% hard, is often considered a "sweet spot" for maximizing the benefits of fitness.

Low-intensity exercise helps build a foundation for aerobic fitness — think 30 minutes or more of jogging or biking at a steady pace that doesn't leave you out of breath or unable to carry a conversation.

Exercising at a high intensity, near your physical limit, can train your body to use more oxygen. One example is doing one minute of an all-out sprint, then resting for two minutes, and repeating for eight total rounds, Thomson said.

It's also a good idea to fit in some strength training, which can prevent injury and help you improve faster at cardio, while also boosting longevity in its own right, research suggests.

How much should you worry about your VO2 max?

The bottom line is that when it comes to fitness and longevity, VO2 max can be a useful metric to help you train for a longer life, but you don't need to spend too much time worrying about the data or comparing your scores to someone else, according to Baird.

"If you're someone who wants to just be healthy and exercise, you don't necessarily have to track VO2 max," Baird said.

If you're not an elite athlete, you can improve your VO2 max over time just by focusing on your work capacity, such as how many miles you can cover before tiring. If you're able to do more over time, or once-challenging workouts start to feel easier, you're on the right track, no lab testing required.

You can also take advantage of VO2 max training regardless of whether you're already athletic, or completely sedentary, just by adding more movement to whatever you're doing now. Every little bit counts, so making time for a few extra minutes of exercise in your daily schedule is like putting money in the bank for the long haul.

"Everyone can improve their VO2 max. Maybe you cannot be the world champion of the marathon, but you can run and you can cycle," Blander said.